Tank arrangement adapted for a submersible pump

Abstract

The present invention relates to a ballast system for a marine structure. The ballast system comprises a ballast tank which is in fluid communication with a tank arrangement for temporarily holding bilge fluid and / or ballast fluid in a marine structure. The tank arrangement comprises a storage space defined by at least one tank wall, at least one fluid inlet for introducing the bilge fluid and / or ballast fluid in the storage space, and at least one fluid outlet permitting removal of at least parts of the bilge fluid and / or ballast fluid from the storage space. The at least one fluid outlet is at least partly formed by a caisson adapted for receiving a submersible pump at a submersible pump position in the storage space.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims benefit of U.S. Provisional Patent Application No. 61 / 179,416, filed on May 19, 2009 and of Swedish Patent Application 0950358-2 filed on May 19, 2009.BACKGROUND[0002]1. Field[0003]The present invention relates to a tank arrangement for a marine structure. The tank arrangement is adapted for a submersible pump, the tank arrangement comprises a circulation conduit for circulating liquid to enable the submersible pump to operate in an advantageous condition substantially at all time. The present invention also relates to an assembly of a submersible pump and a tank arrangement.[0004]2. Background of the Invention[0005]A marine structure, such as a ship or a semi-submersible unit, is often provided with one or more ballast systems in order to control the draught and / or the inclination of the marine structure. Generally, a ballast system comprises a ballast tank, and in fact often a plurality of tanks, which is adapted...

AI Technical Summary

Benefits of technology

[0012]The present invention provides for a tank arrangement which can be utilized with a submersible pump. The tank arrangement enables a submersible pump for pumping e.g. bilge water or ballast water while being constantly submerged in water, thereby removing the risk of failure during start up due to air in the pump, or insufficient pump fluid. By having a tank arrangement which is adapted for a submersible pump, and by using a submersible pump, the tank arrangement is less susceptible for the risks involved when pump rooms are flooded, e.g. during a hull breach. Thus, bilge water and / or ballast water pumping becomes less exposed for failure due to flooding of the pump. The tank arrangement can be operated to separate air entering the storage space together with the incoming liquid, to be a temporarily storage chamber for circulation liquid and to maintain the a predetermined minimum level of liquid in the storage space, enabling the submersible pump to be substantially constantly submerged.

[0025]As used herein, the expression “priming” relates to the removal of air from the low side of a pump, to enable a substantially normal water level in the pump, which in turn enables a substantially normal operation of the pump.

Problems solved by technology

However, in some operations, intrusion of air cannot be avoided.

For example, when a ballast tank is drained of water, there is a risk that air, at low tank level in the ballast tank, will be mixed with ballast water and guided towards to, and later introduced into the pumps such that air will be entrained in the water filling assembly and—at a later stage—in at least a portion of the pump assembly.

As such, when a ballast tank is to be emptied of water, there is a risk that the air in the pump assembly will be guided towards the pump and hence introduced in the pump.

Since air generally adversely affects a pump, the presence of air is undesired.

Since a pump generally has an optimum operating condition at a specific combination of the flow rate and pressure, the aforesaid change in the water flow is generally undesired.

Pumping ballast water usually requires relatively high capacity pumps while when pumping bilge water, generally low capacity pumps are required.

The difference in requirements of the pumps tends to be burdensome for the manufacturer of the marine structure as it demands two different pumps, each specifically adapted for the operating condition required for the specific purpose of the pump.

Further, if the marine structure is damaged, it remains vital that the ballast pumps and bilge water pumps are operational, even if the hull is breached or the space at which the pumps are positioned is flooded.

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